Roll housing with a closed frame construction

ABSTRACT

The present invention relates to a roll housing with a closed frame construction, particularly for heavy roll stands for rolling sheet metal and strip. The roll housing includes two vertical members which delimit the housing window for accommodating and guiding chucks which support the roll. The vertical members have inner surfaces parallel to one another. Upper and lower traverse bars connect the vertical members. The outer sides of each vertical member, which are remote from the housing window, recede toward the housing window between the upper and lower traverse bars such that the shortest distance between the inner surface and outer surface of each of the two vertical members is at a middle position between the upper and lower traverse bars.

FIELD OF INVENTION

The present invention relates to a roll housing with a closed frameconstruction, especially for heavy roll stands for rolling sheet metaland strip. The roll housing comprises two housing uprights, whichdelimit the housing window for accommodating and guiding the roll chucks(and roll bearings). The two housing uprights also have inner surfacesthat are parallel to each other. Upper and lower traverses connect theuprights.

BACKGROUND OF THE INVENTION

Conventional rolling mills consist basically of two roll housings, inwhich the rolls, which run in bearings that are supported by chucks, arearranged. The two housings are connected to each other at the top andthe bottom by transverse connecting parts. The transverse connectingparts and the housings constitute the roll stand. The housings, asconstructive bearing parts of the roll stand, absorb all of the forcesarising during the rolling process. The housings must therefore havehigh strength with low deformation and, at the same time, must permit anadvantageous arrangement of all of the elements of the stand. For heavyrolling mills, one-piece housings with a closed frame construction arepreferred.

As stated above, the housing windows that remain between the housinguprights accommodate the chucks for the bearings of the rolls. Thehousing windows must therefore be equipped with guides, on which thechucks can move in a sliding fashion. For this reason, exact parallelismis required between the inner surfaces (which are located across fromeach other) of the housing windows. Also required are narrow distancetolerances, so that the kinetic play between the chucks and the housinguprights is minimized, ensuring only slight size deviations in therolled material.

In designing roll housings, especially the closed housings describedabove, it is important to consider the fact that, during the rollingprocess, the resultant force is oriented roughly vertical to the rollforce. This means that the total system is subjected to two equalforces, which act in opposite directions and seek to press the traversesapart from each other. In calculatory terms, a closed housing can beseen as an elastic frame, in which a tensile force (half as great, forexample, as the roll force) acts in the vertical direction in thecross-section of the housing uprights, while at the same time a bendingmoment acts on the corners of the housing (FIG. 2). The traverses, whichare connected fixedly to the housing uprights, are stressed exclusivelyby bending. It is assumed that the greatest stress in the housing existson the housing uprights in the window areas, because--along with thetensile stresses--these uprights are bent in the direction of thewindows by the effective bending moment. The housing window is "necked,"i.e., the empty space between the inner sides of the uprights becomessmaller as the result of the roll load.

Since the required rigidity of the roll stand must be guaranteed, everydesigner attempts to ensure that "necking," as the bending of thehousing uprights in the direction of the window is called, is kept to aminimum.

It is easily understood that excessive necking in a roll stand causesthe chucks to jam and interferes with their controllability. It isimpossible to enlarge the clearance between the chucks and the innersurfaces of the windows, because doing so would impair the stability ofthe chuck guidance, and size deviations would occur in the rolledmaterial as a result. For these reasons, necking in rolls stands oftenmakes it necessary to retrofit the windows, which entails largeexpenditures of time and money.

Various proposed solutions to minimize necking in roll stands have, inpractice, been only conditionally effective. For example, an attempt hasbeen made, by enlarging the traverses, to reduce the moment that bendsthe housing uprights. Moreover, the housing uprights themselves havebeen enlarged, so as to counteract their bending with greater resistancemoment. In both cases, the roll stands became heavier and required morematerial, so that the stands also became very expensive. An attempt hasalso been made to reduce the rigidity of the housing frame by means ofundercuts in the corner areas of the housing windows and thus tosimulate a roll stand with practically "articulated joints" between thetraverses and the uprights. However, such undercuts significantlyweakened the stability of the roll stand in these areas, withoutbringing the desired success.

SUMMARY OF THE INVENTION

Starting from the described problems, the object of the presentinvention is to design a closed-frame roll housing in such a way thatthe necking of the housing window between the housing uprights thatresults from the roll forces is reduced to an acceptable level, while atthe same time stress concentrations in the housing are avoided.

To attain this object, the invention proposes that, for the purpose ofreducing the cross-sectional areas of the uprights, the outer sides ofeach upright (which face away from the housing window) recede, startingat the traverses, in the direction of the housing window. The smallestcross-sectional area of the upright will thus be located in the middlearea between the upper and lower traverses.

Tests have shown that the constructive recession in the outer sides ofthe housing uprights can significantly reduce the necking of the housinguprights in the direction of the window. Contrary to previousassumptions, which held that the stability of the roll stand could beincreased--and thus the necking of the housing window reduced--by meansof an enlarged housing cross-section, it has been found that when thecross-section of each upright is reduced as described on the outer sideof the upright, i.e., the side that faces away from the window, thisreduction in cross-section leads to the desired object.

Preferably, the outer side of each upright is provided with a concavecontour in its longitudinal direction, so that the cross-sectional areaof each upright decreases continuously from the upper and lowertraverses to the middle area of the upright.

According to a special feature of the invention, the cross-sectionalreduction is describable by a circular-arc-shaped contour runninglongitudinally on the outer side of each housing upright. The radiusmidpoint of the circular arc that describes the contour is located inthe middle area outside of the upright.

It is also possible for the outer side of each housing upright to havelongitudinal contours in the shape of a parabola or, for example,corresponding to the deflection curve of a carrier on two supports.

It is also conceivable, in the framework of the invention, for the outersides of each upright to be embodied as longitudinal contoursdescribable by progressions; in the extreme case, the polygon could beformed by three points.

The special shape of the housing uprights according to the inventionresults in substantial advantages compared to the known roll stands.Necking in the central area of the housings can be reduced to roughlyzero, so that expensive retrofitting is no longer necessary. This savestime and money, as does the higher availability of the roll stand. Thechucks can be guided in the housing window within very narrowtolerances, and the improved chuck guidance as well as the calmerbearing run result in substantially reduced size deviations in therolled material. The axial load of the roll bearings declines due toreduced twisting of the rolls. The invented measures are extremelysimple and are associated with material savings in the housingsthemselves.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of the disclosure. For a better understanding of the invention, itsoperating advantages, and specific objects attained by its use,reference should be had to the drawing and descriptive matter in whichthere are illustrated and described preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference numerals denote similar elementsthroughout the several views:

FIG. 1 is a simplified three-dimensional depiction of a closed-frameroll housing according to the prior art;

FIG. 2 shows the necking and bending of a housing window of a prior artroll housing expected under a roll load;

FIG. 3 shows a roll housing according to the present invention;

FIG. 4 is a diagram of horizontal necking in roll housings according tothe prior art and according to the present invention;

FIG. 5 is a bar chart comparing the maximum relative stresses andvertical expansions of housings according to the prior art and thepresent invention;

FIG. 6 is a three-dimensional diagram of necking in a roll housingaccording to the present invention, at roll forces between 0 and 100%,relative to the height of the roll housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a closed-frame roll housing of the type described as theprior art in the introductory part of the description. The roll housingas a whole is identified by reference number 1. The roll housing 1comprises two housing uprights 2 and 3, which are connected to eachother by an upper transverse 4 and a lower traverse 5. A housing window6 is located in the interior of the closed frame created by this housingdesign. Inner surfaces 7 of the housing window 6 are located on thehousing uprights 2 and 3. These inner surfaces 7 are flat and lie onparallel planes with respect to the opposite housing upright 2 or 3. Theupper traverse 4 of the roll stand 1 has a boring for a pressure nut,which is not significant in connection with the present invention. Asthe drawing shows, the cross-sections of the housing uprights 2 and 3are the same size between the upper traverse and the lower traverse.Housing window 6 of roll housing 1 receives chucks which support thebearings of rolls in a rolling mill (neither the chucks, the bearings,nor the rolling mill are shown in the figures).

FIG. 2 shows, in schematic fashion, the deformation of the roll housing1 that occurs when the vertical roll forces Y and Y' bend apart theupper and lower traverses 4, 5 of the roll housing 1. The housinguprights 2 and 3 bend inward, as the dashed line 8 shows, reducing theempty space of the housing window 6. The extent of this reduction insize of the housing window 6 depends on the size of the effective forcesY and Y' on the dimensions L1 and L2 of housing traverses 4 and 5 andhousing uprights 2 and 3, and on their resistance moments J₁.

It has been shown that the extent 9 of the bending or necking of thehousing uprights 2, 3 can be significantly reduced and will approachzero when, according to the proposal of the invention, the housingelements 2 and 3 are narrowed in the direction of the housing window 6,as shown in FIG. 3. For example, the outer sides 10 of the housinguprights 2 and 3 are provided with a contour described by a circular arcwith radius R, the midpoint of the circle with radius R being located onan imaginary horizontal line that passes through a center 11 of the rollhousing 1 outside of the housing. In the example, the radius R isselected in such a way that the extent of recession in the two housinguprights 2 and 3 is approximately 30% of the non-necked upright inFIG. 1. For purposes of calculation, the example assumes a roll housingwith a total height of 14,900 mm and an upright with a thickness of 960mm. The assumed height of the lower and upper traverses is 2300 mm. Avariant 1 of the present invention includes a constructive recession onthe outer side 10 of each of the two housing uprights 2 and 3 of 250 mm.A variant 2 of the present invention includes a constructive recessionof 295 mm on the outer side 10 of each of the two housing uprights 2 and3.

FIG. 4 shows, in diagram form, the extent of horizontal necking relativeto housing height. The solid line represents the necking of the priorart roll housing. The line with longer dashes represents Variant 1(i.e., with a recession of 250 mm). The line with shorter dashesrepresents Variant 2 (i.e., with a recession of 295 mm). The drawingclearly shows that, in the case of the uprights not embodied accordingto the present invention, horizontal necking of almost 2 mm can beexpected in the middle of the housing. Both Variant 1 and Variant 2display significantly reduced necking over the entire housing height. Inthe case of Variant 2 (i.e, with a recession of 295 mm), necking in themiddle area of the housing approaches zero even at 100% roll load.

This finding is confirmed by the bar chart in FIG. 5. This diagramclearly indicates that the embodiment of the roll housing according tothe invention reduces the relative stress of 72.6 N/mm² in the prior artto 67.8 N/mm² in Variant 2. Although there is a slight verticalexpansion of the housing, from 2.13 to 2.39 mm, in the direction of theeffective forces Y and Y', this vertical expansion of the roll housing,compared to the necking of the housing window, is harmless andnegligible.

FIG. 6 shows the horizontal necking in a roll housing according to theinvention in a three-dimensional diagram and in dependence on the rollforce percentage. Here, too, a significant reduction in necking, whichapproaches zero, can be seen even at 100% roll force. A roll housingaccording to the present invention thus attains the stated object in asimple manner.

The invention is not limited by the embodiments described above whichare presented as examples only but can be modified in various wayswithin the scope of protection defined by the appended patent claims.

I claim:
 1. A roll housing having a closed frame construction,comprising:first and second housing uprights, each having an innersurface and an outer surface; upper and lower traverses connecting upperends and lower ends of said first and second housing uprights; a housingwindow, being delimited on its sides by said inner surface of each ofsaid first and second housing uprights, for receiving chucks forsupporting bearings of rolls; said inner surface of one of said firstand second housing uprights being parallel to said inner surface of theother of said first and second housing uprights; and said outer surfaceof each of said first and second housing uprights, which faces away fromsaid housing window, receding toward said housing window between saidupper and lower traverses such that a shortest distance between saidinner surface and said outer surface, of each of said first and secondhousing uprights is at a position between said upper traverse and saidlower traverses, said receding of said outer faces toward said housingwindow substantially reduce necking of said first and second uprights ina direction toward said housing window.
 2. The roll housing with aclosed frame construction of claim 1, wherein said outer surface of eachof said first and second housing uprights has a concave contour runningin a longitudinal direction of said uprights.
 3. The roll housing with aclosed frame construction of claim 1, wherein said outer surface of eachof said first and second housing uprights has a circular-arc-shapedcontour running in a longitudinal direction of said uprights.
 4. Theroll housing with a closed frame construction of claim 1, wherein saidouter surface of each of said first and second housing uprights has aparabolic contour running in a longitudinal direction of said uprights.5. The roll housing with a closed frame construction of claim 1, whereinsaid outer surface of each of said first and second housing uprights hasa contour describable by progressions in a longitudinal direction ofsaid uprights.